refactor: clarify configuration merging

Author: pvdlg

lib/load-parser-config.js

@@ -12,14 +12,14 @@ const conventionalChangelogAngular = require('conventional-changelog-angular');
  * @return {Promise<Object>} a `Promise` that resolve to the `conventional-changelog-parser` options.
  */
 module.exports = async ({preset, config, parserOpts}) => {
-  let loadedConfig = {};
+  let loadedConfig;
 
   if (preset) {
     const presetPackage = `conventional-changelog-${preset.toLowerCase()}`;
     loadedConfig = importFrom.silent(__dirname, presetPackage) || importFrom(process.cwd(), presetPackage);
   } else if (config) {
     loadedConfig = importFrom.silent(__dirname, config) || importFrom(process.cwd(), config);
-  } else if (!parserOpts) {
+  } else {
     loadedConfig = conventionalChangelogAngular;
   }
 
@@ -28,10 +28,10 @@ module.exports = async ({preset, config, parserOpts}) => {
   } else {
     loadedConfig = await loadedConfig;
   }
+
   return mergeWith(
     {},
-    loadedConfig.parserOpts,
-    parserOpts,
+    !preset && !config && parserOpts ? parserOpts : {...loadedConfig.parserOpts, ...parserOpts},
     (value, source) => (Array.isArray(value) ? source : undefined)
   );
 };